WO2008065631A1

WO2008065631A1 - Method and composition for treating water

Info

Publication number: WO2008065631A1
Application number: PCT/IB2007/054871
Authority: WO
Inventors: Joanne Raphael Katz; David Arthur Baldwin
Original assignee: Joanne Raphael Katz; David Arthur Baldwin
Priority date: 2006-11-30
Filing date: 2007-11-30
Publication date: 2008-06-05

Abstract

The invention provides for a chemical composition for treatment of water, the chemical composition comprising a mixture which includes a persulphate compound such as sodium persulphate, a monopersulphate compound such as 5 potassium monopersulphate, a pH buffer, a zinc compound and a transition metal compound. The transition metal of the transition metal compound is copper, silver, manganese or iron. The pH buffer is sodium bisulphate. The invention extends to a method of treating water by admixing the composition with raw water to be treated.

Description

METHOD AND COMPOSITION FOR TREATING WATER

THIS INVENTION relates to a chemical composition for treatment of water to enhance the purity thereof, for example, to a level suitable for humans to bathe in. The invention also relates to a method of treating water to enhance the purity thereof.

According to a first aspect of the invention there is provided a chemical composition for treatment of water, the chemical composition comprising a mixture which includes:

20 - 80% by mass of a member selected from a group consisting of alkali metal persulphates, ammonium persulphate, hydrates of alkali metal persulphates, hydrates of ammonium persulphate and mixtures thereof;

20 - 80% by mass of a member selected from a group consisting of potassium monopersulphate, hydrates of potassium monopersulphate and mixtures thereof;

1 - 20% by mass of a pH buffer;

1 - 20% by mass of a zinc compound; and

2 - 20% by mass of a member of a group consisting of transition metal compounds and mixtures thereof, each transition metal compound of the group being soluble in water and forming a transition metal ion which is able to cycle between two oxidation states when the composition is added to water, whose pH is buffered by the pH buffer to maintain it in the range of 6.8 - 8.4. The pH buffer may be a bisulphate such as sodium bisulphate. The composition may include 7 - 17 % by mass of sodium bisulphate.

The zinc compound may be a zinc salt, for example a member of a group consisting of zinc sulphate, zinc chloride and mixtures thereof. The zinc compound preferably forms 1 ,3 - 3,3% by mass of the composition.

The composition may include up to 10% by mass of a filter aid selected from a group consisting of diatomaceous earth, natural zeolites, synthetic zeolites and mixtures thereof.

Further, the composition may include up to 20% by mass of a solid flocculent selected from a group consisting of aluminium sulphate, aluminium chloride, aluminium hydroxychloride and an organic polymer flocculant.

The transition metal compound may be complexed with a complexing agent selected from a group consisting of amine complexing agents, organic carboxylic acid complexing agents and mixtures thereof.

It is expected that, typically, the oxidation states will be the (I) and (II) oxidation states, or the (II) and (III) oxidation states. In particular, the transition metal of the transition metal compound may be a member selected from copper (having the (II) and (III) oxidation states), silver (having the (I) and (II) oxidation states), manganese (having the (II) and (III) oxidation states), iron (having the (II) and (III) oxidation states) and mixtures thereof. Preferably, the transition metal is a member of a group consisting of copper, silver and a mixture thereof.

5

Without being bound by theory, the applicant believes that the addition of a transition metal compound provides transition metal cations which catalyse the formation of free radicals from persulphate ions (S₂O₈ ^2"), organic material then being oxidised by the free radicals thus formed. More particularly, if the transition metal i o cation cycles between two numerically adjacent states, the applicant believes that the following reactions take place:

S₂O₈ ^2" + Mⁿ⁺ → M^{(n+1 )+} + SO₄ ^2" + SO₄-^" (I)

M⁽ⁿ⁺¹⁾⁺ + H₂O → Mⁿ⁺ + H⁺ + HO- (II) where Mⁿ⁺ is the transition metal ion (which may be complexed), in its lower adjacent 15 oxidation state, M^{(n+1 )+} is the transition metal ion in its adjacent higher oxidation state and S₂O₈ ^2" is the persulphate ion. These reactions are thought to be similar to those promoted by iron ions, copper ions and enzymes containing iron or copper in biological systems.

20 Thus reaction (I) leads to the production of highly reactive sulphate radicals (SO₄ ^2"-) and reaction (II) leads to the production of highly reactive hydroxy radicals (OH-), both of which can be regarded as highly reactive free radical oxidizing agents which can kill microorganisms and react with organic pollutants to reduce the offensiveness thereof.

As indicated above, the transition metal ion of the transition metal compound is preferably one having a lower adjacent oxidation state in which it is a member of a group consisting of Cu²⁺, Ag^{1 +}, Mn²⁺ and Fe²⁺, more preferably Cu²⁺, and/or Ag^{1 +}, its upper adjacent oxidation state being, respectively, Cu³⁺, Ag²⁺, Mn³⁺ and Fe³⁺, as the case may be.

As also indicated above, the transition metal compound may be complexed with an amine complexing agent or an organic carboxylic acid complexing agent for increasing the solubility of the transition metal compound in water. The amine complexing agent may be a member of a group consisting of ethylenediaminetetra-acetic acid (EDTA), nitrilotriacetic acid (NTA), ethanolamine, diethanolamine, triethanolamine and mixtures thereof.

It should be noted that, while the transition metal compounds and the persulphates or hydrates thereof participate in the free-radical forming reactions set forth above, the function of the monopersulphate or its hydrates is to provide the water with an initial shock treatment, the monopersulphate acting as a powerful and rapid oxidising agent. The transition metal ions are considered to also promote the rate of reaction of the monopersulphate anion.

The flocculant and the filter aid are added to the mixture to aggregate small suspended or colloidal particles that can often otherwise pass through normal filter mediums, thereby to assist filters to remove these particles. This improves the colour and clarity of the water, assists in removing bacteria and algae that often bind to suspended matter, increases the aesthetic appeal of the water and improves safety by ensuring that swimmers can readily see the sides and the bottom of swimming pools which contain water which has been treated with the composition.

The invention extends to a method of treating water to enhance the purity thereof, the method comprising the step of admixing, with raw water to be treated, a composition as described and defined above.

The Applicant envisages that a dosage of the composition of 2.5 - 10mg/l per litre of raw water will be required to purify water to a level suitable for humans to bathe in, depending upon the contamination of the water. The treatment is preferably applied weekly.

During treatment, when invention is being used to treat swimming pool water, the pH of the water is preferably maintained in the range 6.8 - 7.2. In addition, the alkalinity is preferably maintained at a level of 50 - 80 ppm, the alkalinity being increased to the correct level by the addition of sodium bicarbonate or soda ash, and a calcium ion concentration is preferably maintained at a level of 250 - 350 ppm, preferably 200 ppm. The calcium ion concentration may be increased to the correct level by the addition of, say, calcium chloride. Without limitation to the application of the invention, the applicant envisages that, in addition to the treatment of swimming pool water, the invention can be of use in the treatment of water for spas, the treatment of water for industrial use and the treatment of water for human consumption.

The treatment of water as set out above is preferably supplemented from time to time with an additional shock treatment in which a chemical composition is added to the water to be treated, the composition for shock treatment comprising a mixture which includes:

20 - 80% by mass of a member selected from a group consisting of alkali metal persulphates, ammonium persulphate, hydrates of alkali metal persulphates, hydrates of ammonium persulphate and mixtures thereof; and

20 - 80% by mass of a member selected from a group consisting of potassium monopersulphate, hydrates of potassium monopersulphate and mixtures thereof.

The composition for additional shock treatment may include a chlorine containing compound. The composition for additional shock treatment may include up to 40% by mass of the chlorine containing compound, depending on the contamination of the water. The chlorine containing compound is preferably one of the solid hypochlorite compounds such as trichloroisocyanurate, sodium dichloroisocyanurate, potassium dichloroisocyanurate, lithium hypochlorite or chloro- p-toluene sulphonamide or a mixture thereof.

The additional shock treatment is preferably applied at the beginning of a bathing season, and thereafter from time to time as and when the water requires further treatment in addition to the weekly treatment with the composition containing the transition metal compound as described and defined above.

The invention is further described hereinafter by way of a non-limiting Example.

Example

A chemical composition for the treatment of water to enhance the purity thereof to a level suitable for humans to bathe in, in accordance with the invention, comprises a mixture of the following compounds in the following proportions, by mass:

Sodium persulphate (Na₂S₂O₈) 38%

Potassium monopersulphate (KSO₅) 39% Sodium bisulphate 7%

Copper sulphate (CuSO₄) 2%

Alumino-silicates i.e. zeolites (supplied under the name "Decolite") 4%

Aluminium Sulphate 8% Zinc sulphate (ZnSO₄) 2%

The composition was used to treat water in a swimming pool. The composition was applied at a dosage of 6mg/l per litre of water. During treatment,

5 the pH of the water was maintained at 6.9, with the alkalinity of the water being maintained at 45 ppm and the water having a calcium ion concentration which was maintained at 200 ppm.

To enhance the purity of the water to make it suitable for humans to i o bathe in, the treatment of water as set out above is supplemented from time to time with an additional shock treatment in which a chemical composition is added to the water to be treated, the composition for shock treatment comprising a mixture which includes the following compounds in proportion by mass:

15 Sodium Persulphate 30%

Potassium Monopersulphate 30% Sodium Dichloroisocyanurate 30% Aluminium Sulphate 10%

20 The treatment was found to keep the water clear and substantially bacteria-free for a period of a week, with no objectionable taste or odour.

Unlike chlorine-based disinfectants, a composition for treatment of water in accordance with the invention, as described and illustrated, avoids the production of harmful trihalomethanes and chlorophenols and results in a reduced concentration of harmful phenols, the composition for additional shock treatment which includes the chlorine-containing compound being used only occasionally, if and when needed. Moreover, water treated by the invention furthermore results in cleaner water and has no objectionable taste or odour. It is believed that the copper sulphate and the zinc sulphate act synergistically with each other to produce an enhanced algaecidal effect.

Claims

1 . A chemical composition for treatment of water, the chemical composition comprising a mixture which includes: 20 - 80% by mass of a member selected from a group consisting of alkali metal persulphates, ammonium persulphate, hydrates of alkali metal persulphates, hydrates of ammonium persulphate and mixtures thereof;

1 - 20% by mass of a pH buffer;

1 - 20% by mass of a zinc compound; and

2 - 20% by mass of a member of a group consisting of transition metal compounds and mixtures thereof, each transition metal compound of the group being soluble in water and forming a transition metal ion which is able to cycle between two oxidation states when the composition is added to water, whose pH is buffered by the pH buffer to maintain it in the range of 6.8 - 8.4.

2. A composition as claimed in Claim 1 , in which the pH buffer is a bisulphate.

3. A composition as claimed in Claim 2, in which the bisulphate is sodium bisulphate.

4. A composition as claimed in Claim 3, in which the composition includes

7 - 17 % by mass of sodium bisulphate.

5. A composition as claimed in Claim 1 , in which the zinc compound is a zinc salt.

6. A composition as claimed in Claim 5, in which the zinc salt is a member of a group consisting of zinc sulphate, zinc chloride and mixtures thereof.

7. A composition as claimed in Claim 5, in which the zinc compound forms 1 ,3 - 3,3% by mass of the composition.

8. A composition as claimed in Claim 1 , in which the composition includes up to 10% by mass of a filter aid selected from a group consisting of diatomaceous earth, natural zeolites, synthetic zeolites and mixtures thereof.

9. A composition as claimed in Claim 8, in which the composition includes up to 20% by mass of a solid flocculent selected from a group consisting of aluminium sulphate, aluminium chloride, aluminium hydroxychloride and an organic polymer flocculant.

10. A composition as claimed in Claim 1 , in which the transition metal compound is complexed with a complexing agent selected from a group consisting of amine complexing agents, organic carboxylic acid complexing agents and mixtures thereof.

1 1 . A composition as claimed in Claim 1 , in which the transition metal of the transition metal compound is a member selected from a group consisting of copper, silver, manganese, iron and mixtures thereof.

12. A composition as claimed in Claim 1 1 , in which the transition metal is a member of a group consisting of copper, silver and a mixture thereof.

13. A composition as claimed in Claim 10, in which the amine complexing agent is a member of a group consisting of ethylenediaminetetra-acetic acid (EDTA), nitrilotriacetic acid (NTA), ethanolamine, diethanolamine, triethanolamine and mixtures thereof.

14. A method of treating water to enhance the purity thereof, the method comprising the step of admixing, with raw water to be treated, a chemical composition for treatment of water, the chemical composition comprising a mixture which includes:

20 - 80% by mass of a member selected from a group consisting of alkali metal persulphates, ammonium persulphate, hydrates of alkali metal persulphates, hydrates of ammonium persulphate and mixtures thereof; 20 - 80% by mass of a member selected from a group consisting of potassium monopersulphate, hydrates of potassium monopersulphate and mixtures thereof;

1 - 20% by mass of a pH buffer; 1 - 20% by mass of a zinc compound; and

15. A method as claimed in claimed in Claim 14, in which the pH buffer is sodium bisulphate.

16. A method as claimed in Claim 14, in which the zinc compound is a member of a group consisting of zinc sulphate, zinc chloride and mixtures thereof.

17. A method as claimed in Claim 14, in which the transition metal compound is complexed with a complexing agent selected from a group consisting of amine complexing agents, organic carboxylic acid complexing agents and mixtures thereof.

18. A method as claimed in Claim 14, in which the transition metal of the transition metal compound is a member selected from a group consisting of copper, silver, manganese, iron and mixtures thereof.

19. A method a claimed in Claim 14, in which a dosage of the composition of 2.5 - 10mg/I per litre of raw water is used.

20. A method as claimed in Claim 14, in which the pH of the water is maintained in the range 6.8 - 7.2.

21 . A method as claimed in Claim 14, in which the alkalinity of the water is maintained at a level of 50 - 80 ppm.

22. A method as claimed in Claim 14, in which a calcium ion concentration in the water is maintained at a level of 250 - 350 ppm.

23. A method as claimed in Claim 14, in which the treatment of water is supplemented from time to time with an additional shock treatment in which a chemical composition is added to the water to be treated, the composition for shock treatment comprising a mixture which includes: 20 - 80% by mass of a member selected from a group consisting of alkali metal persulphates, ammonium persulphate, hydrates of alkali metal persulphates, hydrates of ammonium persulphate and mixtures thereof;

20 - 80% by mass of a member selected from a group consisting of potassium monopersulphate, hydrates of potassium monopersulphate and mixtures thereof; and a chlorine containing compound.

24. A method as claimed in Claim 23, in which the composition for additional shock treatment includes up to 40% by mass of the chlorine containing compound.

25. A method as claimed in Claim 24, in which the chlorine containing compound is a member of a group consisting of trichloroisocyanurate, sodium dichloroisocyanurate, potassium dichloroisocyanurate, lithium hypochlorite, chloro-p- toluene sulphonamide and mixtures thereof.